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Full text of "The Cambridge Natural History"

164

AMERICAN   EDENTATES

sentatives  have as jet been discovered which can be referred, to
the Anteater, Armadillo, or Sloth type with certainty.1

Of these American forms, which will "be treated of "first, the
Armadillos are further apart from either Sloths or Anteaters
than the last two are from each other. The name XENARTHRA
has been suggested for the American Edentates with " abnormal "
vertebral articulations; the corresponding NQMAKTHRA includes
the Old-World forms.

Between the Sloths and Anteaters the extinct Megatherium
and some of Its allies are to a certain
extent Intermediate. But It may be
pointed out In the first place that there
are certain Important resemblances be-
tween the living forms. In both, retia
rnirabllla are developed In the tail (in
spite of its reduction In the Sloths) and
In the limbs, But, as is well known,
retia are also found In other mammals
far removed in the series from these
under consideration. The reproductive
organs generally are very similar, and
they have both a dome-shaped and
deciduate placenta. The latter char-
Q 90 ^BigM scapula and ciavi- aeter they share with the Armadillos

cle of Two-toed Sloth (Choloepv*              -,•.,-.         *       j  -rr     i       ™-      •    i

hojftnanni).    x if.    a   Aero-  and with, tne Aard Vark; Jaams hav-

f co^ ;lTr"^; in§ a »«»****>*» ?*•«»<» **&* «.

coraco - scapular foramen.; gc, like that of the Oamivora, zonary In
fi>™- The Edentates, at any rate the
American forms, have a double vena

cava posterior and no  azygos vein.     This condition is also met
with among Whales.

Oateologically the Sloths and Anteaters are united by the
fact that the coracoid becomes fused with the coracoid border
of the scapula, thus forming a foramen; the importance of this
character is, however, discounted by its occurrence in three
genera of Cebidae.

The above facts embody the views of Sir William  Flower.2

1 A rather problematical  Armadillo, ATecrodasypws,  has l>een  recorded   from
French strata.     It consists of a few scutes only.
3 JVoc, Zool. 8oc. 1882, p. 358,